[canana]

Yes, you should never yell at your dogs. Others shouldn't either. I don't think there is such a thing as spiteful aggression.

'Stay', 'come', and 'down' are essentials. 'Come' needs to be reinforced at every chance you get and just know that some dogs never have 100% recall.
Walking politely on a leash is a must if you go for daily walks.
If you can train 'bark' and 'quiet', those are great commands.

I'd start with those first and forget about house guests for now. If you have guests, keep him contained in a separate space. Or if you feel he won't bark aggressively, keep him on a leash but tethered to you at all times.

My thoughts on Cesar Milan is that his techniques may be useful for rehabilitative works. I doubt your dog is at that stage. I do however believe that as a dog owner, I am the leader of the pack. Dogs are mentally more happy and stable when they know they need to look to you for direction. I've watched Zak George videos and he seems to have a better approach. My favourite is Kikopup's videos - she gets to the point much faster.

With your family and in-laws. Well...focus on training your dog first. Worry about them later. You don't really need to worry about what they think of your training tactics. It can be a pointless battle. Once you have your dog nice and trained up, they won't care how you did it.